This invention relates generally to nuclear reactor, and more particularly to a service platform for use in a nuclear reactor.
A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide, sometimes referred to as a grid is spaced above a core plate within the RPV. A core shroud, or shroud, surrounds the core plate and is supported by a shroud support structure. The core shroud is a reactor coolant flow partition and structural support for the core components. Particularly, the shroud has a cylindrical shape and surrounds both the core plate and the top guide. A removable head is coupled to a head flange at the top of the shroud.
During refueling of a nuclear reactor, the majority of the servicing operations are performed from a bridge system that spans the refueling floor and the reactor and fuel storage pool cavities. These bridges typically have a straight four to eight foot wide walkway along their length and can be positioned above the reactor or refueling pool cavity. The refuel bridge must be elevated about five feet above the floor surface to clear the hand rails and other structures at the edge of the reactor cavity or service pools.
When in use, the bridge is moved to the desired position above the reactor permitting personnel to work along the walkway of the bridge. When working over a round reactor vessel, access to a specific azimuth zone of the round reactor vessel is limited by the shape of the bridge. With existing bridge access, the number of work activities, and number of personnel that can perform work at the same time is limited.
The type of work required to service a nuclear plant would be enhanced by simultaneous access to the reactor along the radial and tangential directions of the vessel or component. A normal bridge system positioned over a reactor can only accomplish radial or tangential alignment at two locations. Furthermore, both radial and tangential alignment can never be accomplished simultaneously. Therefore, personnel and equipment may not have the optimal angle of access for visual observation or equipment and component manipulation.